1. FIELD OF THE INVENTION
This invention relates to a simplified, potentially low cost system for applying drywall tape, which has been precoated on both sides thereof with a wet adhesive mud, during the installation of gypsum wallboard.
2. BACKGROUND ART
The repetitive and laborious process of taping drywall has led to several systems of taping, each of which having serious limitations. Since the advent of drywall technology, the taping of the seams that are created when sheets of drywall are nailed in place has been a pedestrian exercise that requires the handling of paper tape and wet adhesive mud. Such paper tape and adhesive mud are presently sold separately, such that the mud is not applied to the paper tape prior to use. In the time consuming manual application of the paper tape, the adhesive mud is manually scooped out of a container and applied with a smearing action to drywall seams with a drywall knife. The paper tape is then unrolled so as to be laid upon the seam and wiped down into the wet mud. The tape is later top coated with more mud and wiped smooth after each coat to flatten the tape surface. In the conventional time consuming, manual taping method just described, one layer of mud is applied under the paper tape to achieve adhesion, and at least two additional layers of mud are commonly applied over the tape to embed the tape within the mud. The top layers of mud are applied and wiped down until the mud appears smooth and the gap between the drywall sheets is made flat. The mud should be allowed to dry between successive coats.
One well known commercial taping system is sometimes known as the Ames system. The Ames system consists of a series of tools that are designed to handle both dry, non-adhesive paper tape and wet adhesive mud to make the tape applying procedure faster than if it were manually completed. The tools of the Ames system generally consist of a manual mud pump, a taping tool, a roller, finishers and a standard drywall knife. Many of the Ames tools are complex, relatively expensive and require extensive training, adjustment and manual dexterity to operate. In the Ames system, the drywall mud is pumped out of a bucket into a cylinder within the Ames taping tool. This taping tool holds a roll of dry paper tape. When the cylinder of the taping tool is full of mud, the taping tool is held against the seam to be taped and the head of the taping tool is rolled along the seam. The taping tool cylinder is emptied of the mud as a wheel on the taping tool head, which contains a pulley, reels up a steel cable that is attached to a piston within the cylinder. The mud then exits the taping tool through a hole at the head as dry paper tape is rolled onto the mud as it is ejected on the wall. The seam must be wiped down with a drywall knife to complete the taping operation. The seam then requires a top coat of mud to fully embed the tape. With the Ames system, full embedding occurs only after three operations: applying tape and mud to the drywall seam; wiping the tape down; and then top coating the seam.
The aforementioned tool shave various limitations and shortcomings. The Ames system is very expensive and requires many unique parts which must be machined and maintained in proper adjustment. The taping tool is heavy and difficult to use, and requires that many precision parts operate in the hostile environment of gritty adhesive viscous drywall mud. The tool must be cleaned, oiled and adjusted often so as not to break down or become jammed or stop working. Parts have been known to wear out and break, thereby requiring substantial maintenance and expense. Moreover, the Ames taping tool system does not apply mud to the top side of the drywall tape.
A more primitive taping tool called a "banjo" utilizes a reel of dry tape that is threaded through a chamber of wet mud as the tape exits the tool. The muddy tape is then applied directly to the drywall seam and wiped down manually. Since the banjo concentrates all of the mud under the tape, very little mud is applied to the back side of the tape. With a banjo taping system, another coat of mud must be applied to fully embed the tape. What is more, the banjo is slow and inefficient, inasmuch as the mud may not properly and fully coat the underside of the tape, thereby leaving a dry blister. The banjo is heavy and awkward to use and requires that the muddy tape be wiped down after it is unrolled on the drywall seam. What is more, a banjo will not tape inside corners easily.
It would therefore be desirable to have an effective labor saving drywall taping system that is inexpensive to manufacture, easy to use and light in weight. The system should be able to operate in the hostile environment of the adhesive mud materials and not be adversely affected by the mud drying and/or a failure to thoroughly clean the tools after each use. The system should also utilize materials and procedures that are common to the drywall taping industry. It would be further desirable to reduce the occurrence of air blisters which are occasionally formed under the tape. The system should be able to fully embed the drywall tape during the initial application, thus reducing the number of required steps and eliminate much of the labor associated with conventional taping procedures.